Electron multiplier



Oct. l; 1946. v F, A.1. G. vAN DEN BcscH 2,408,709

ELECTRON MULTIPLIER Filed Aug. 10, 1942 BY .Hau A/zav ATToR/vgy 'pendent Y `upon vthe v Patented Oct. 1, 1946 ELEc'raoN MULTIPLIER Francois Joseph' Gerard van denosch, Surrey, ',England, assigner to Radio Electronics Lim- Application August 10,

TheY invention 'relates'. 'to apparatus primarily for dealingwith ultra-high frequencies butV applicable also for ldealingwith lwer'frequencies.' n y According tothis invention'an electron multiplier comprisesa number of pairs of electrodes for controlling the Velocity of the electrons (hereinafter 'referred to as velocity-controlling pairs of electrodes) disposed ink the stream of electrons betweena'pimary/ cathode and an anode, one or more secondary cathodes also disposed in said streamJneans for generating an alternating field between the electrodes of each velocity-con- V trolling pair,the distance apart between adjapairs being selectedV cent electrodes ofsuccessive in accordancewitl'ithe'phaserelationship of their potentials, so that the time of transit of an Velectron fis such thatv it passesthrough a succeeding field approximately at the same stage inthe cycle as that when it passed through the "preceding field. l

The, alternating elds may be applied to said pairs of velocity-controlling electrodes so that the adjacent electrodes of successive pairs are in phase'and at equal potentials while the two alternating iields produced by`said adjacent pairs are 180 out of phase,l thespacing apart of equipotential' electrodes being' such as to 'provide' a time of transit corresponding te thetime vof half a vcycle'or multiples thereof. Alternatively, fthe alternating field vbetween. each pair of velocitycontrollng electrodes may 'tained 'at a following secondary cathode -of the multiplier since the secondary emission is deelocity of the electrons imvpinging onft'her secondary cathode. `Alternativ`e1y,OI in"addition,other Iknown means may be employed to obtainthe required conversion. Furthermore', either or both of the electrodes vof'-a"velocity-controllingpair of electrodes may "beconstitnted by a secondary cathode, since the y be provided by con-- necting the electrodes through suitable imped- 1942, rseriali No. 454,214 InAGreat Britain August 5, 1940 y s'olwaims. e (ci. 25o-27) r 2 eiect of a secondary cathode is to arrest the slower velocity electrons, while thek impact of the higher.' velocity 'electrons will release additional electrons."

-Thejiollowing is a'description of two embodiments of the'inventio reference being made to th accompanying drawing, A in which- Y Figure 1 and Figure 2 are diagrammatic views each showing diagrammatically an electron multipli'er, together with its external circuit.

According to the construction shown in Figure 1, the electron multiplier isv provided with a primary cathode ID and secondary electron-emitting cathodesvII, I2, I3, I4, I5 and 22. Acontrolgrid II i'sprovidedbetween the primary cathode and Y therstsecondary cathode I I, and a final collectinganode rIt is provided at the back of the last secondary cathode 22. The primary electron stream may be modulated by a modulator I9 connected to the control grid, and the potential of the grid may be biased through one part 28 ofa potentiometer whichis connected at suitable tapping points along its length to the secondary cathodes. It vwill be seen that in front of the secondary cathode I2 is disposed a pair of Velocitycontrollingpelectrodes 2I and I8, while a second pair of velocity-controlling electrodes Y23 and 24 are provided at the back of the electrode. The two electrodes I8 and' 23 are both connected to one poleofvan valternator A8, whereas the electrodesf2IA and 24 of theV alternator. The secondary cathodel I2 is ternating fields betweeny the electrodes 2l and I8 and between the electrodes 23 and 24 are, however, 180 out of phase.v Thus, in order to-effect velocity modulation, -the time of transit of an electron between the electrodes I8 and 23 should ybe equivalent to half the time of a complete cycle of the alternating generator, or odd multiples thereof. Although the secondary cathode I2 has the effect of arresting the low-velocity electrons, the secondary electrons released by it do not upset the velocity modulation.

The next two-secondary cathodes I3 and I4 Vare grouped together, and-have on one side thereof a pair of velocity-modulating electrodes 24 and 25, and on the otherside thereof a pair of ,velocity-modulating electrodes 26 and 21. Again, in this instance, the adjacent electrodes 25 and 26 of the two pairs are connected to one pole of k Athe alternator, Whereas theelectrodes 24 and 2`l are connected to the other pole. Similarly, the

ysecondzjn'ycathode I5 has two -pairs of velocityccintrailingelectrodes,v one pairpn.Vv each side are connected to the other pole 3 thereof, viz., the electrodes 2'! and 28, and the electrodes 29 and 3i), the electrodes 28 and 29 beinsr connected to one pole of the generator, and the electrodes 27 and 3) being connected to the other pole. A dual antennae 'l is either connected between the,electrode 3i] and the two electrodesl 28 and 29 or between the electrode 30 and the anode i6 as shown in the drawing. One side of the dual antennae could either be connected to the secondary cathode 22 or to the anode as shown in Figure l. In any of these arrangements) the secondary cathode 22 may operate to convert` the velocity modulation to density .modulationas set out above. In the arrangement shown in Figure 2, the

alternating eld between the variousN pairs ort, velocity-controlling electrodes is obtained byconnecting each electrode through a suitable imped- ,I

ance to a terminal of the alternator. The secondary cathode 3| is arranged in an equipoten- 20 tial eld betweenrelectrodes v32; 33, which 'are connected through a variable impedance 34 to a. terminal of the alternator 8. Velocity modulation doesnottake place until afterthis electrode. The next Vsecondary cathode,` 35; however, has'a pair of velocity-controlling electrodes 'on each side thereof, viz., the lectrodes 33 and 36, and the electrodes 3lA and 38. Alternating Yiields are created between the electrodes of each pair by reason ofthe fact thatthe electrode 33 is 'connected through a variable impedance 34" with the a1- tern'ator, and the "electrode 38 lis connected through `a different variable vimpedance 39 with' said alternator. Similarly, `the electrodes '3'1v vand 33 are connected throughv the diierent variable impedances .3S and d. The secondary cathodes tif-and 42 each have a pair of velocity-controlling electrodes oneach Vside thereof,.'in the one case thejpairsri, 38Vand 63, M and inthe other case, thegelectrodes 43, 44 and the electrode 45 and the secondary cathode 22, a further variable im-l pedance i6 being provided between the equipotentialelectrcdes 4d and 45' andthe alternator. Ingthe two arrangements referredto above the velocity-,controlling electrodes are shown as ordil nary grids; these, however, could'be replaced by secondary cathodes. v fljclaimz ,1,n Anfelectron multiplierY apparatus comprising aA primary cathode,v an anode, a number f'pair's ojf ,velocity-controlling `electrodes fand atleast onesecondary cathode disposed between 'the pri'- inary cathode and anode, means -for"applying direct rcurrent potentials of ascending "orde'r'to said primary cathode, secondary cathode 'and ancde,ni eans `ior applying an alternating'f'eld between the electrodes ci each pair oi velocitycontrolling electrodes, the distance apart between electrodes of successive pairs of velocity-controlling electrodes being `selected in accordance with thephase relationship of their 'potentials s'o' that the transit time of an electron is such'th'at it passes through a succeeding rleldl at approximately the same stage inthe "cycle 'as that when it passed through the preceding field.

2. An'electron multiplier 'apparatus compris- 55 ing a primarycathode, an anode, a number of 'pairs of velocity-controlling 'electrodes and at lea-st on'e secondary-cathode disposed between the primary cathode and'anode, means for applying direct current potentials of ascending order to said primary cathode, secondary cathode and anode,means for applying an alternating, eld between the electrodesof each pair of velocityvcontrolling.electrodes so that adjacent electrodesk of successive pairs are in phase and at equal po- 7.5

tentials, while the two alternating elds produced by two adjacent pairs are 180 out of phase, the spacing apart of the electrodes being such as to provide a time of transit of an electron between equipo-tential electrodes corresponding to the time of odd multiples of half a cycle including a single half-cycle and tocause said electron to pass through a succeeding eld at-approximately the same stage in the cycle as that when it passed through the preceding field.

' 3. An electron multiplier apparatus comprising a primary cathode, an anode, a number of pairslcf velocity-controlling electrodes and at least one secondary cathode disposed between the primary cathode and anode, an alternator arvranged -to apply an alternating eld between the electrodes-fof Veach pair of velocity-controlling electrodes, means for applying direct current potentials of ascending order to said primary cathode, secondary cathode and anode, an impedaviricve-tconnected rbetween saidy alternator and each jpair `of, said velocityecontrolling electrodes, the values-of which impedances are selected s o neldsfproduced 'by twov adjacentpairs of'electrodesare *180 out of phase that the two alternating andthe spacing Aapart of the electrodes `of the two pairs being 'such as to 'provide a timeV ofA transit'of an' electron betweenthe'adja'cent elec- Y trode's of two pairs corresponding tc'the 'time of an'odd multiple'of half a' cycle 'including halia cycle and Ato cause said electron'to pass 'through a succeeding AIield atapproximatelythejsaid stage in the cycle as that when itpassed through ltne preceding 'field VLnn electron multiplier apparatus comprising 'a 'primary cathode, an anode, a number of pairs 'of velocity-controlling electrodes disposedinthe stream ofV electrons between the primary cathode 'and anode, at 'least Vone 'secondary cathode arranged between adjacent electrodes of successive pairs of velocity-.controlling electrodes,r means tor applying direct current '.potentials'of ascending orders to said primary cathode, secondary cathode and' anode, means for applying anY alternating neld between the electrodes vof each pairfof velocity-'controlling electrodes, the distance apart vbetween 'electrodes' 'of successive pairs of` velocity-controlling `electrodes being selected 1in accordance with the 'phase relationship "of their potentials so "that the time 'of transit ofanelectron i's such that it passes Ythrough va succeeding eldat approximately the same stagevin thecycle' als vthat when it lpassed.tlfiro'ugh the `preceding held. v

- 5. An `electron multiplier apparatus comprising a primary cathode, anA anode-a;Y numbercf pairs of. velocity-controlling electrodes disposed in -a'stream of electrons between the primary cathode andanode, atleas't one secondary cathode disposed between Veach'pair of velocity-controlling electrodes, a secondary cathode immediately preceding said anode, an outputl 'circuit associated with said secondary cathode, 'means 4for applying potentials of ascending -order to said ,primary cathode, vsecondary "cathode 'and anode, -mea'nsffor applying an alternatingeld v'between .theelectrlo'des of each pair of velocitycontrolling electrodes, rthe distance rapart .between electrodes of successive pairs of velocity-controlling electrodes being slectd'inlaccordance Vwith the phase relationship ofv theirlptentials Sothat the time of transitY of4 an electron is 'such' `that Ait passes through a succeeding held/'atv 'approxii ately-thesame stage in the cycle as that when Ait passed through the preceding'leld.

6 ity-controlling electrodes, the distance apart be- 6. An electron multiplier apparatus compristween electrodes of successive pairs of velocitying a primary cathode, an anode, a number of pairs of velocity-controlling electrodes disposed controlling electrodesbeing selected in accordin the stream of electrons between the primary ance with the phase relationship of their potencathode and anode, one of which Velocity-con- 5 tials so that the time and transit of an electron trolling electrodes in each pair being formed as is such that it passes through a succeeding eld a secondary cathode, means for applying direct at approximately the same stage in the cycle as current potentials between the primary cathode and anode, means for applying an alternating FRANCOIS JOSEPH GERARD eld between the electrodes of each pair of veloc- 10 vAN DEN BOSCH.

that when it passed through the preceding eldf 

